Add patches to make C and Cpp packages installable

[scarabeusiv]

As the package is now used by libreoffice we at SUSE needed to be able to safely install the package on the distribution while avoiding conflicts.

Fixes issues #61 and #63

[scarabeusiv]

Generated package as a proof of concept:
https://build.opensuse.org/package/show/LibreOffice:Factory/QR-Code-generator

[nayuki]

I appreciate your individual commits with helpful messages, instead of one big unauditable mess.

Thanks for informing me that my library is being used in a popular open-source software package, LibreOffice.

I do have some fears that some of the changes you propose might only be appropriate for a particular platform (e.g. Linux vs. BSD) or for a particular distribution (e.g. SUSE-specific conventions or constructs).

I will allocate some time in the coming days to understand the proposed changes and what effects they have. I will certainly solicit you with questions during my audit if there's something I don't understand.

[lwhsu]

This PR seems have conflicts now. @scarabeusiv , do you have a plan to rebase this? Thanks.

[scarabeusiv]

@lwhsu rebased.

[xvitaly]

@nayuki Can you merge this?

[ilya-fedin]

Any progress?

[heirecka]

I do have some fears that some of the changes you propose might only be appropriate for a particular platform (e.g. Linux vs. BSD) or for a particular distribution (e.g. SUSE-specific conventions or constructs).

I can't talk about any of the BSDs (but I suspect it's the same for them, too) but I'm pretty sure every distribution wants install targets with a way to pass PREFIX and DESTDIR. So I added the patches from this PR to my distro's packaging.

[ilya-fedin]

Makefiles from this PR are more Linux- and BSD-friendly than the current one, I guess.

[ilya-fedin]

1,5 weeks and this PR can celebrate that it is open for 8 months 🧐

[ilya-fedin]

@nayuki friendly ping

[xvitaly]

This PR need to be rebased to version 1.6.0 btw.

[powpingdone]

@nayuki another ping, this PR should probably get merged. These new makefiles look fine.

[xvitaly]

Implemented CMake build and installation support: https://github.com/EasyCoding/qrcodegen-cmake

git clone https://github.com/nayuki/QR-Code-generator.git qrcodegen
git clone https://github.com/EasyCoding/qrcodegen-cmake.git qrcodegen-cmake
cp -f qrcodegen-cmake/CMakeLists.txt qrcodegen/
mkdir -p qrcodegen/build
cd qrcodegen/build
cmake ..
cmake --build .

@nayuki I can send a PR with CMake support if you want.